Continuous fiber winding reinforced polyethylene composite pipe and preparation method thereof

Abstract

The invention relates to the technical field of composite pipelines, in particular to a continuous fiber winding reinforced polyethylene composite pipe and a preparation method of the continuous fiber winding reinforced polyethylene composite pipe. The fiber reinforced layer is wound on the inner-layer polyethylene pipe, the outer polyethylene protective layer is wound outside the fiber reinforced layer, and the outer reinforced pipe is wound on the surface of the outer polyethylene protective layer. The continuous fiber winding reinforced polyethylene composite pipe prepared by the invention has excellent flexibility, the production process is simple, the production efficiency is high, and all production procedures of multi-layer compounding can be realized through one station.

Description

Technical Field

[0001] This invention relates to the field of composite pipe technology, specifically to a continuous fiber-wound reinforced polyethylene composite pipe and its preparation method. Background Technology

[0002] Currently, prestressed steel cylinder cement pipes, ductile iron pipes, and welded steel pipes are mainly used in the medium and large diameter pipeline application market. However, these pipe products all have some defects. For example, the prestressed steel wires in prestressed steel cylinder cement pipes are prone to breakage, causing pipeline failure, and the pipes are also heavy, resulting in high construction and installation costs. Metal pipes cannot be used for underground burial in environments with corrosive acids, alkalis, and salts, and their corrosion resistance and flexibility in resisting foundation settlement are poor. Compared with prestressed steel cylinder cement pipes and metal pipes, polyethylene pipes have the advantages of good corrosion resistance, strong compressive strength, and light weight, but their rigidity is low and their pressure-bearing capacity is poor.

[0003] Wrapping fiberglass tape around the surface of polyethylene pipes is an effective method to improve their rigidity and tensile strength. However, the current production method for fiberglass tape reinforcement layers in the industry involves first winding the inner base pipe, then hoisting the mold with the wound base pipe to another station for the fiber tape winding process. Furthermore, the winding is only done unidirectionally along one side of the base pipe, without cross-winding, resulting in poor stability of the winding composite process and a high risk of delamination failure of the reinforced composite layer. The existing process also lacks the technique of axially arranging the fiber reinforcement layer along the base pipe, leading to insufficient axial tensile strength of the polyethylene pipe. After the fiber reinforcement layer is wound, the roller mold needs to be hoisted again to the extrusion process for winding the protective layer and the outer pressure-resistant reinforcement tube. This method of repeatedly hoisting the roller mold not only wastes time and results in low production efficiency, but also causes significant heat loss during hoisting and is highly prone to problems with weak composite welding. Furthermore, in the existing technology, the abrupt transition between the socket section and the straight pipe section at approximately 45° angle without a gentle slope design makes it difficult for the fiber to be wound onto the socket section. Even if it is forcibly wound, the sudden change in angle will prevent the fiber from adhering well to the pipe body, which seriously affects the feasibility of the production process and the quality of the final product.

[0004] Patent CN119081271A discloses a weather-resistant and anti-aging polyethylene pipe and its preparation method. The pipe uses high-density polyethylene resin, linear low-density polyethylene resin, polyimide resin micropowder, nano-silica, nano-hexagonal boron nitride, polybenzimidazole fiber, oxalic acid, zinc glycyrrhizate, antioxidant 1010, hindered amine light stabilizer, polydimethylsiloxane titanate crosslinked polymer, and 3-methacryloyloxypropyltriethoxysilane as raw materials. Specifically, the polyimide resin micropowder, oxalic acid, and zinc glycyrrhizate are mixed evenly, and then modified at 300℃-350℃ for 30-60 minutes to obtain a modified product, which significantly improves the pipe's weather resistance and anti-aging properties. The components are well-matched, and the special modification preparation method better leverages the synergistic effect of the components, greatly improving the weather resistance and anti-aging properties of the polyethylene pipe. However, this formula has problems such as high cost and complex processing technology. Among them, nanomaterials such as nano-silica and boron nitride are prone to agglomeration, while polyimide and polybenzimidazole have very poor compatibility with polyethylene. Furthermore, the processing temperature of the former two is higher than that of polyethylene, which may cause some polyethylene to degrade.

[0005] Patent CN104448488A discloses a fiber-reinforced polyethylene pipe material, prepared from the following raw materials in parts by weight: polyethylene resin, carbon black, fiber, compatibilizer, coupling agent, lubricant, and antioxidant; the fiber is one or more of surface-treated glass fiber, carbon fiber, and basalt fiber; the fiber length is 1-8 mm. The compatibilizer is maleic anhydride-grafted polyethylene; the coupling agent is one of silane coupling agent, titanate coupling agent, and aluminate coupling agent; the lubricant is one of acetal amide, calcium stearate, zinc stearate, stearic acid, and polyethylene wax; the antioxidant is a compound of hindered phenolic antioxidant 1010 or 1076 and phosphite antioxidant 168. It possesses good mechanical properties, excellent weather resistance, high strength, aging resistance, good safety, and long service life. However, adding a large amount of fiber filler during polyethylene processing increases melt viscosity, which affects the processing performance of the raw material. While the addition of fibers improves tensile strength and stiffness, it also leads to a decrease in the toughness, ductility and compressive strength of the material.

[0006] Therefore, there is an urgent need in the market for a polyethylene composite pipe with excellent rigidity and pressure resistance, reliable pipe joint quality, and high production efficiency. Summary of the Invention

[0007] In view of the problems existing in the prior art, the purpose of this invention is to obtain a continuous fiber-wound reinforced polyethylene composite pipe with excellent rigidity and compressive strength, strong adhesion between layers, consistent structural strength in all parts of the pipe, and high production efficiency.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention provides a continuous fiber-wound reinforced polyethylene composite pipe, which consists of an inner polyethylene pipe, a fiber reinforcement layer wound on the inner polyethylene pipe, an outer polyethylene protective layer wound on the outside of the fiber reinforcement layer, and an outer reinforcement pipe wound on the surface of the outer polyethylene protective layer.

[0009] Another aspect of the present invention provides a method for preparing a continuously fiber-wound reinforced polyethylene composite pipe, comprising the following steps: S1. Add the core polyethylene material to the core tube extruder, pre-embed an electric heating wire at the socket end of the core tube die, preheat the core tube die with gas flame, and melt and extrude at 170-220℃ to obtain the inner layer polyethylene tube. Wrap the fiber tape on the inner layer polyethylene tube through a forward and reverse circumferential cross-winding and axial multi-layer winding composite unit to form a fiber reinforcement layer. Add the outer layer polyethylene material to the extruder, and extrude and wind composite on the surface of the fiber reinforcement layer to form an outer polyethylene protective layer, resulting in a three-layer fiber-reinforced polyethylene composite pipe with inner and outer polyethylene tubes and a fiber reinforcement layer in the middle. S2. Add polypropylene material to a single-wall corrugated pipe extruder, add polyethylene material to the extruder, and co-extrude at 200-220℃ to obtain an outer reinforced pipe with a polypropylene inner layer and a polyethylene outer layer. S3. The outer reinforcing tube obtained in step S2 is wound around the fiber-reinforced polyethylene composite tube obtained in step S1 to obtain a continuous fiber-wound reinforced polyethylene composite tube.

[0010] Preferably, the polypropylene layer in the outer reinforcing tube has a thickness of 2-4 mm, and the polyethylene layer has a thickness of 1.5-6 mm.

[0011] This application realizes all production processes of multi-layer composite in one station. By setting grooves for embedding resistance wires on the outside of the mold socket end, the resistance wires can be pre-laid on the core tube mold, solving the problem of resistance wire arrangement and maintenance, improving thermal efficiency, ensuring uniform heat distribution, and thus improving product quality. This application also achieves bidirectional reinforcement in both circumferential and axial directions by winding fiber tape onto the inner polyethylene tube through a forward and reverse circumferential cross-winding and axial multi-layer winding composite unit, which helps to improve the compressive strength of the product.

[0012] In some embodiments, the core tube polyethylene material comprises, by weight, the following raw materials: 60-90 parts high-density polyethylene, 2-6 parts compatibilizer, and 0.1-1 parts antioxidant.

[0013] In some embodiments, the method for preparing the compatibilizer includes the following steps: A1. Add hexagonal boron nitride and KH-550 silane coupling agent to an ethanol aqueous solution, sonicate at 40-50℃ for 40-60 min, and dry to obtain modified hexagonal boron nitride. A2. Mix itaconic acid, dicumyl peroxide and linear low-density polyethylene evenly in a high-speed mixer, add the modified hexagonal boron nitride and sodium hypophosphite obtained in step A1, mix evenly to obtain a mixture; A3. Add the mixture obtained in step A2 into a twin-screw extruder and extrude it at 170-190℃ to obtain the final product.

[0014] In some embodiments, the mass ratio of the hexagonal boron nitride to the KH-550 silane coupling agent is 1:(0.05-0.15).

[0015] This application uses itaconic acid-modified linear low-density polyethylene to prepare a compatibilizer containing a large number of carboxyl groups. Adding this compatibilizer to the core tube polyethylene material can enhance the interaction between the glass fiber and the core tube, and strengthen the adhesion between the fiber reinforcement layer and the inner and protective layers, which is beneficial to improving the rigidity and internal pressure bearing performance of the composite pipe.

[0016] This application further incorporates modified hexagonal boron nitride during the compatibilizer preparation process. The carboxyl groups on itaconic acid-modified linear low-density polyethylene can form hydrogen bonds with the hydroxyl and amino groups on hexagonal boron nitride, resulting in good compatibility of hexagonal boron nitride in polyethylene materials. The nano-hexagonal boron nitride sheets possess high strength and modulus. Uniformly dispersed within the polyethylene matrix, they act as a supportive "skeleton," restricting the movement of polymer chain segments and thus improving the elastic modulus and tensile strength of the composite material. When the material is subjected to impact, the uniformly dispersed nano-hexagonal boron nitride sheets can induce crimping and deflect crack paths, effectively absorbing and dispersing impact energy, potentially improving compressive strength. Nano-hexagonal boron nitride also possesses certain barrier properties, preventing oxygen and moisture from entering the pipe interior, thereby improving the aging resistance and corrosion resistance of the core tube.

[0017] In some embodiments, the mass ratio of itaconic acid to linear low-density polyethylene is (0.05-0.15):1.

[0018] In some embodiments, the mass ratio of modified hexagonal boron nitride to linear low-density polyethylene in step A2 is (0.04-0.08):1.

[0019] In some embodiments, the antioxidant is composed of a primary antioxidant and a secondary antioxidant, wherein the primary antioxidant is one or more of 1010, antioxidant 1076, and antioxidant 330; and the secondary antioxidant is antioxidant 168 or antioxidant 626.

[0020] In some embodiments, the fiber tape is one or more of glass fiber tape pre-impregnated with polyethylene resin, carbon fiber tape pre-impregnated with polyethylene resin, and aramid fiber tape pre-impregnated with polyethylene resin.

[0021] In some embodiments, the inner polyethylene tube has a thickness of 6-20 mm, the fiber reinforcement layer has a thickness of 0.6-9 mm, and the outer polyethylene protective layer has a thickness of 6-20 mm.

[0022] In some embodiments, the core tube mold includes a straight tube section, a transition section, and a socket end; the transition section has a sloping structure with a slope angle of 2-7°; and the length of the transition section is 500-1500 mm.

[0023] This application provides a transition section at the connection between the straight pipe section and the socket, which ensures that the fiber is shaped before shrinking and demolding after being wound in the socket. This allows the fiber to fit well into the pipe body, solving the problem of adhesion between the multiple layers of the fiber reinforcement layer and between the fiber reinforcement layer and the inner and protective layers, thus ensuring that all parts of the pipeline maintain the same structural strength.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention realizes all production processes of multi-layer composite through one station, and by setting grooves for embedding resistance wires outside the socket mold, the resistance wires are pre-laid on the roller mold. The socket mold part adopts the internal expansion method design. After the socket is wound and shaped, it shrinks and demolds, which solves the problem of adhesion between the multi-layer composite of the fiber reinforcement layer and between the inner layer and the protective layer. It also solves the process problem of composite reinforcement in the positive and negative circumferential and axial directions of the fiber reinforcement layer, and realizes the function of bidirectional reinforcement in both circumferential and axial directions.

[0025] (2) By using itaconic acid to modify linear low-density polyethylene, the compatibilizer prepared contains a large number of carboxyl groups. Adding it to the polyethylene material of the core tube can enhance the interaction between the glass fiber and the core tube, and enhance the adhesion between the fiber reinforcement layer and the inner layer and the protective layer, which is beneficial to improving the rigidity and internal pressure bearing performance of the composite pipe.

[0026] (3) In this invention, the carboxyl group on the prepared itaconic acid modified linear low-density polyethylene can have hydrogen bonding with the hydroxyl and amino groups on the hexagonal boron nitride, which makes the hexagonal boron nitride have good compatibility in polyethylene materials, thereby improving the rigidity, compressive strength, corrosion resistance and aging resistance of polyethylene composite pipes. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the core tube mold structure; 1. Straight pipe section; 2. Transition section; 3. Socket end.

[0028] Figure 2This is a photograph of the continuous fiber-wound reinforced polyethylene composite pipe of Example 1. ① Inner polyethylene pipe; ② Fiber reinforcement layer; ③ Outer polyethylene protective layer; ④ Polypropylene layer; ⑤ Polyethylene layer. Detailed Implementation

[0029] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0030] In the following examples and comparative examples, except for the compatibilizer, all other compounds and related reagents used were commercially available. The high-density polyethylene (HDPE) was grade 041 and purchased from Shanghai Petrochemical; the polypropylene material was model PPB-M02 and purchased from Shanghai Petrochemical; the glass fiber tape of the preimpregnated polyethylene resin was grade GE60473-01 and purchased from Qingdao CIMC Chuangying Composite Materials Technology Co., Ltd.; the hexagonal boron nitride was model BN-1 and purchased from Qinghe County Beiyan Metal Materials Co., Ltd.; and the maleic anhydride-grafted low-density polyethylene was grade NF358E and purchased from Mitsui Chemicals.

[0031] The color of the continuous fiber wound reinforced polyethylene composite pipe can be adjusted by adding different color masterbatches according to actual needs, without special limitations. In the following examples, the core polyethylene material, outer polyethylene material, polyethylene material, and polypropylene material have been colored by conventional methods.

[0032] Preparation Example 1 The preparation method of compatibilizer-1 includes the following steps: A1. Add 60g of hexagonal boron nitride and 6g of KH-550 silane coupling agent to 300g of 80wt% ethanol aqueous solution, sonicate at 45℃ for 50min, and dry to obtain modified hexagonal boron nitride. A2. Mix 100g itaconic acid, 10g dicumyl peroxide and 1000g linear low-density polyethylene evenly in a high-speed mixer, add 60g of modified hexagonal boron nitride obtained in step A1, mix evenly to obtain a mixture. A3. Add the mixture obtained in step A2 into a twin-screw extruder and extrude it at 180°C to obtain the final product.

[0033] Preparation Example 2 The preparation method of compatibilizer-2 is the same as that of preparation example 1, except that the amount of itaconic acid added is 200g.

[0034] Preparation Example 3 The preparation method of compatibilizer-3 is the same as that of preparation example 1, except that the amount of modified hexagonal boron nitride added in step A2 is 100g.

[0035] Preparation Example 4 The preparation method of compatibilizer-4 includes the following steps: A1. Mix 100g itaconic acid, 10g dicumyl peroxide and 1000g linear low-density polyethylene evenly in a high-speed mixer to obtain a mixture; A2. Add the mixture obtained in step A1 into a twin-screw extruder and extrude it at 180°C to obtain the final product.

[0036] Preparation Example 5 The preparation method of compatibilizer-5 includes the following steps: A1. Add 60g of hexagonal boron nitride and 6g of KH-550 silane coupling agent to 300g of 80wt% ethanol aqueous solution, sonicate at 45℃ for 50min, and dry to obtain modified hexagonal boron nitride. A2. Mix 1000g of maleic anhydride-grafted low-density polyethylene and 60g of hexagonal boron nitride obtained in step A1 in a high-speed mixer to obtain a mixture. A3. Add the mixture obtained in step A2 into a twin-screw extruder and extrude it at 180°C to obtain the final product.

[0037] Example 1 Reference Appendix Figure 1 Appendix Figure 2 A method for preparing a continuous fiber-wound reinforced polyethylene composite pipe includes the following steps: S1. Add the polyethylene core material to the core tube extruder, pre-embed heating wires at the socket end 3 of the core tube mold, preheat the core tube mold with gas flame, melt and extrude at 190℃ to obtain an inner polyethylene tube ① with a thickness of 12mm. Wind glass fiber tape pre-impregnated with polyethylene resin onto the inner polyethylene tube ① through a forward and reverse circumferential cross winding and axial multi-layer winding composite unit to form a fiber reinforcement layer ② with a thickness of 8mm. Add the outer polyethylene material to the extruder, extrude and wind composite on the surface of the fiber reinforcement layer ② to form an outer polyethylene protective layer ③ with a thickness of 6mm, to obtain a three-layer fiber-reinforced polyethylene composite pipe with inner and outer polyethylene tubes and a fiber reinforcement layer ② in the middle. S2. Add polypropylene material to a single-wall corrugated pipe extruder, add polyethylene material to the extruder, and co-extrude at 210℃ to obtain an outer reinforced pipe with an inner layer of 3mm thick polypropylene layer ④ and an outer layer of 2mm thick polyethylene layer ⑤. S3. The outer reinforcing tube obtained in step S2 is wound around the fiber-reinforced polyethylene composite tube obtained in step S1 to obtain a continuous fiber-wound reinforced polyethylene composite tube.

[0038] The core tube polyethylene material, by weight, contains the following raw materials: 75 parts high-density polyethylene, 4 parts compatibilizer-1, 0.3 parts antioxidant 1010, and 0.2 parts antioxidant 168.

[0039] The core tube mold includes a straight pipe section 1, a transition section 2, and a socket end 3; the transition section 2 has a sloping structure with a slope angle of 6.46°; the length of the transition section is 570mm.

[0040] Figure 2 This is a photograph of the continuous fiber-wound reinforced polyethylene composite pipe of Example 1.

[0041] Example 2 Reference Appendix Figure 1 Appendix Figure 2 A method for preparing a continuous fiber-wound reinforced polyethylene composite pipe includes the following steps: S1. Add the polyethylene material to the core tube extruder, pre-embed an electric heating wire at the socket end 3 of the core tube mold, preheat the core tube mold with gas flame, and melt and extrude at 170℃ to obtain an inner polyethylene tube ① with a thickness of 12mm. Wind the glass fiber tape pre-impregnated with polyethylene resin onto the inner polyethylene tube ① through a forward and reverse circumferential cross winding and axial multi-layer winding composite unit to form a fiber reinforcement layer ② with a thickness of 8mm. Add the outer polyethylene material to the extruder, and extrude and wind composite it on the surface of the fiber reinforcement layer ② to form an outer polyethylene protective layer ③ with a thickness of 6mm. A three-layer fiber-reinforced polyethylene composite pipe with inner and outer polyethylene tubes and fiber reinforcement layer ② in the middle is obtained. S2. Add polypropylene material to a single-wall corrugated pipe extruder, add polyethylene material to the extruder, and co-extrude at 200℃ to obtain an outer reinforced pipe with an inner layer of 3mm thick polypropylene layer ④ and an outer layer of 2mm thick polyethylene layer ⑤. S3. The outer reinforcing tube obtained in step S2 is wound around the fiber-reinforced polyethylene composite tube obtained in step S1 to obtain a continuous fiber-wound reinforced polyethylene composite tube.

[0042] The core tube polyethylene material, by weight, contains the following raw materials: 60 parts high-density polyethylene, 2 parts compatibilizer-1, 0.06 parts antioxidant 1010, and 0.04 parts antioxidant 168.

[0043] The core tube mold includes a straight pipe section 1, a transition section 2, and a socket end 3; the transition section 2 has a sloping structure with a slope angle of 6.46°; the length of the transition section is 570mm.

[0044] Example 3 Reference Appendix Figure 1 Appendix Figure 2 A method for preparing a continuous fiber-wound reinforced polyethylene composite pipe includes the following steps: S1. Add the polyethylene core material to the core tube extruder, pre-embed an electric heating wire at the socket end 3 of the core tube die, preheat the core tube die with gas flame, and melt and extrude at 220℃ to obtain an inner polyethylene tube ① with a thickness of 12mm. Wind the glass fiber tape pre-impregnated with polyethylene resin onto the inner polyethylene tube ① through a forward and reverse circumferential cross winding and axial multi-layer winding composite unit to form a fiber reinforcement layer ② with a thickness of 8mm. Add the outer polyethylene material to the extruder and extrude and wind composite on the surface of the fiber reinforcement layer ② to form an outer polyethylene protective layer ③ with a thickness of 6mm. A three-layer fiber-reinforced polyethylene composite pipe with polyethylene tubes in the inner and outer layers and fiber reinforcement layer ② in the middle is obtained. S2. Add polypropylene material to a single-wall corrugated pipe extruder, add polyethylene material to the extruder, and co-extrude at 220℃ to obtain an outer reinforced pipe with an inner layer of 3mm thick polypropylene layer ④ and an outer layer of 2mm thick polyethylene layer ⑤. S3. The outer reinforcing tube obtained in step S2 is wound around the fiber-reinforced polyethylene composite tube obtained in step S1 to obtain a continuous fiber-wound reinforced polyethylene composite tube.

[0045] The core tube polyethylene material, by weight, contains the following raw materials: 90 parts high-density polyethylene, 6 parts compatibilizer-1, 0.6 parts antioxidant 1010, and 0.4 parts antioxidant 168.

[0046] The core tube mold includes a straight pipe section 1, a transition section 2, and a socket end 3; the transition section 2 has a sloping structure with a slope angle of 6.46°; the length of the transition section is 570mm.

[0047] Example 4 A method for preparing a continuous fiber-wound reinforced polyethylene composite pipe, the specific implementation method is the same as in Example 1, except that compatibilizer-1 is replaced with compatibilizer-2 in equal amounts.

[0048] Example 5 A method for preparing a continuous fiber-wound reinforced polyethylene composite pipe, the specific implementation method is the same as in Example 1, except that compatibilizer-1 is replaced with compatibilizer-3 in equal amounts.

[0049] Example 6 A method for preparing a continuous fiber-wound reinforced polyethylene composite pipe, the specific implementation method is the same as in Example 1, except that compatibilizer-1 is replaced with compatibilizer-4 in equal amounts.

[0050] Example 7 A method for preparing a continuous fiber-wound reinforced polyethylene composite pipe, the specific implementation method is the same as in Example 1, except that compatibilizer-1 is replaced with compatibilizer-5 in equal amounts.

[0051] Performance testing Test specimens with a length of 200 mm and a width of 25 mm were cut from the fiber-reinforced polyethylene composite pipes obtained in each embodiment for tensile strength testing and fiberglass tape weld strength testing. Hydrostatic tests were performed on the continuously fiber-wound reinforced polyethylene composite pipes. The test methods are shown in Table 1. Table 1

[0052] The test results are shown in Table 2: Table 2

[0053] As shown in Table 2, the continuous fiber-wound reinforced polyethylene composite pipes prepared in Examples 1-3 of this invention have good mechanical properties and compressive strength, and high bonding strength between layers. A comparison between Example 4 and Example 1 shows that changing the ratio of itaconic acid and linear low-density polyethylene may cause itaconic acid to undergo self-polymerization, leading to a decrease in its grafting rate on the polyethylene chain segments, thereby reducing the mechanical properties, bonding strength, and compressive strength of the polyethylene composite pipe. A comparison between Example 5 and Example 1 shows that changing the ratio of modified hexagonal boron nitride and linear low-density polyethylene may cause the modified hexagonal boron nitride to agglomerate and reduce the active carboxyl groups on the compatibilizer, thereby reducing the mechanical properties, bonding strength, and compressive strength of the polyethylene composite pipe. A comparison between Example 6 and Example 1 shows that when the compatibilizer does not contain modified hexagonal boron nitride, its mechanical properties and compressive strength decrease. A comparison between Example 7 and Example 1 shows that when itaconic acid-grafted low-density polyethylene is replaced with maleic anhydride-grafted polyethylene, the mechanical properties, bonding strength, and compressive strength of the polyethylene composite pipe are poor.

[0054] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a continuous fiber-wound reinforced polyethylene composite pipe, characterized in that, Includes the following steps: S1. Add the core polyethylene material to the core tube extruder, pre-embed an electric heating wire at the socket end of the core tube die, preheat the core tube die with gas flame, and melt and extrude at 170-220℃ to obtain the inner layer polyethylene tube. Wrap the fiber tape on the inner layer polyethylene tube through a forward and reverse circumferential cross-winding and axial multi-layer winding composite unit to form a fiber reinforcement layer. Add the outer layer polyethylene material to the extruder, and extrude and wind composite on the surface of the fiber reinforcement layer to form an outer polyethylene protective layer, resulting in a three-layer fiber-reinforced polyethylene composite pipe with inner and outer polyethylene tubes and a fiber reinforcement layer in the middle. S2. Add polypropylene material to a single-wall corrugated pipe extruder, add polyethylene material to the extruder, and co-extrude at 200-220℃ to obtain an outer reinforced pipe with a polypropylene inner layer and a polyethylene outer layer. S3. The outer reinforcing tube obtained in step S2 is wound around the fiber-reinforced polyethylene composite tube obtained in step S1 to obtain a continuous fiber-wound reinforced polyethylene composite tube.

2. The method for preparing a continuous fiber-wound reinforced polyethylene composite pipe according to claim 1, characterized in that, The core tube polyethylene material, by weight, contains the following raw materials: 60-90 parts high-density polyethylene, 2-6 parts compatibilizer, and 0.1-1 parts antioxidant.

3. The method for preparing a continuous fiber-wound reinforced polyethylene composite pipe according to claim 2, characterized in that, The method for preparing the compatibilizer includes the following steps: A1. Add hexagonal boron nitride and KH-550 silane coupling agent to an ethanol aqueous solution, sonicate at 40-50℃ for 40-60 min, and dry to obtain modified hexagonal boron nitride. A2. Mix itaconic acid, dicumyl peroxide and linear low-density polyethylene evenly in a high-speed mixer, add the modified hexagonal boron nitride and sodium hypophosphite obtained in step A1, mix evenly to obtain a mixture; A3. Add the mixture obtained in step A2 into a twin-screw extruder and extrude it at 170-190℃ to obtain the final product.

4. The method for preparing a continuous fiber-wound reinforced polyethylene composite pipe according to claim 3, characterized in that, The mass ratio of the hexagonal boron nitride to the KH-550 silane coupling agent is 1:(0.05-0.15).

5. The method for preparing a continuous fiber-wound reinforced polyethylene composite pipe according to claim 3, characterized in that, The mass ratio of itaconic acid to linear low-density polyethylene is (0.05-0.15):

1.

6. The method for preparing a continuous fiber-wound reinforced polyethylene composite pipe according to claim 3, characterized in that, The mass ratio of modified hexagonal boron nitride to linear low-density polyethylene in step A2 is (0.04-0.08):

1.

7. The method for preparing a continuous fiber-wound reinforced polyethylene composite pipe according to claim 1, characterized in that, The fiber tape is one or more of the following: glass fiber tape pre-impregnated with polyethylene resin, carbon fiber tape pre-impregnated with polyethylene resin, and aramid fiber tape pre-impregnated with polyethylene resin.

8. The method for preparing a continuous fiber-wound reinforced polyethylene composite pipe according to claim 1, characterized in that, The inner polyethylene tube has a thickness of 6-20 mm, the fiber reinforcement layer has a thickness of 0.6-9 mm, and the outer polyethylene protective layer has a thickness of 6-20 mm.

9. The method for preparing a continuous fiber-wound reinforced polyethylene composite pipe according to claim 1, characterized in that, The core tube mold includes a straight tube section, a transition section, and a socket end; the transition section has a sloping structure with a slope angle of 2-7°; the length of the transition section is 500-1500mm.

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